Apparatus for producing wax impregnated corrugated board



April 1962 J. MCK. LIMERICK ETAL 3,031,355

APPARATUS FOR PRODUCING WAX IMPREGNATED CORRUGATED BOARD Filed Sept. 29, 1959 I INVENTORS JACK MCK. LIMERICK WILLEM ANDRE NIKKEL AT TORN-IV United States Patent ()fifice 3,031,355 Patented Apr. 24, 1962 APPARATUS FOR PRODUCING WAX IMPREG- NATED CORRUGATED BOARD Jack McK. Limerick, Westmount Place, Apt. 807, 201

Metcalfe Ave., Westmount, Quebec, Canada, and Willem A. Nikkei, 6917 Lemieux St., Montreal, Quebec, Canada Filed Sept. 29, 1959, Ser. No. 843,262

1 Claim. (Cl. 156-490) It is an object of this invention to provide a doublefaced corrugated board which will be resistant to liquid moisture as Well as moisture vapor, and which will have greater stacking strength than ordinary, untreated corrugated board of the same makeup of liners and corrugating medium.

It is a further object of this invention to provide a method and apparatus for making a board as aforesaid.

It is a further object of this invention to provide a method and apparatus as aforesaid which may be merged into normal operations of forming standard corrugated board without adding extraneous operations and without slowing the normal operations of such equipment.

The above and other objects will be made clear from the following detailed description, taken inconnection with the annexed drawing in which FIGURE 1 is a schematic diagram of the method and apparatus aforesaid.

Increasingly in late years there has been a demand for containers formed of corrugated board for such varied uses as the packaging of meat and poultry, fruits and fresh produce, and other uses in which the container must withstand not only high humidity for prolonged periods, but also actual liquid moisture. When considered merely as sheets, there has never been any particular difiiculty in rendering a sheet such as kraft liner board and corrugating medium resistant to water in both the liquid and vapor phases. When so treated, however, it has been impossible to form, between the two liners and the corrugating medium an adhesive bond sufiicient to provide the requisite strength in the combined structure. This problem has been met heretofore by forming ordinary corrugated sheets, coating the outer faces of the liners heavily with wax, then stacking the coated sheets in an oven for a period (rather long) sufficient to cause the wax to penetrate the liners and the corrugating medium. This is, of course, an operation wholly extraneous to ordinary board manufacture and adds greatly to the cost of the final impervious board.

It long has been known that certain papers, e.g.: kraft 0.009" corrugating, can be semi-impregnated with asphalt and still have adhesive receptive surfaces, while at the same time having a high degree of resistance to water in both the liquid and vapor phase. An example of this treatment may be found in Patent No. 2,767,091. Of course it is not intended to limit the present case to the disclosure of that patent. Asphalt lends itself far better to this purpose than do most waxes and resins, but has the disadvantage of having an adverse effect on color. This latter effect, of course, has no bearing on the use of the treated paper as a corrugating medium, especially for double-faced corrugated.

Briefly, the present invention contemplates the use of a corrugating web treated, by whatever means so as tobe moisture resistant While still receptive to adhesive. This is combined, quite as usual, with a standard liner board to form single-faced corrugated. The outer surface of the liner is then heavily coated with wax. Simultaneously the outer liner board is being coated on what is to be its outer surface with an equally heavy coating of wax. Both boards then are subjected to preheating, the single-faced corrugated board is then combined with the opposite liner board, again quite as usual, and the combined boards are just as resistant to both liquid and vaporized moisture as the corrugating medium.

As used herein, the term wax is more generic than its definition in ordinary texts on organic chemistry. That is, the wax may be of the ester type, the parafiin type, or a synthetic equivalent of either. The only requirements are: that under heat it will liquify; that in the liquid phase it will impregnate a fibrous web, and that, on cooling, the impregnated web will be highly resistant to moisture in both vapor and liquid phases. The term resistant as used herein has a meaning somewhat different than its usual connotation in the packaging industry. Here the resistance is primarily to a wetting or weakening of the component sheets of the board and secondarily to the passage therethrough of liquid or vapor. The secondary consideration, however, is, nevertheless important.

As noted above, the chemical nature of the Wax is waxes is not too sharply defined, and this blurring of the melting point increases, usually, in blends of waxes. Any stated melting point, therefore, must be considered as a median between extremes of several degrees on each side of the stated melting point.

In yet another respect the melting point is not critical. The optimum melting point depends on web speed and on available heat. These latter factors are also mutually dependent, i.e.: as web speed increases, more heat must be made available. For any given combination of web speed and available heat there is a required maximum melting point for the wax. Obviously, also, the minimum melting point must be one well above any temperature which the board may be expected to encounter in use. In practice melting points Will run, usually, from about F. to about 200 F.

Theoretically, web speeds may be anything greater than zero. In practice, however, about 30 feet per minute will produce about as expensive a board as any mill can expect to sell, while about 300 feet per minute is just about all that may be expected of even the best of present day equipment.

A further point on terminology is this: impregnation with wax to the extent of 30% to 40% of the fibre content of the board yields a product 23% to 25% of wax in the final product. Throughout this application the first given percentages will be used, namely wax as a percent of the fibre content. The percentages, of course, by weight.

Referring now to FIGURE 1, a web 10 of single-faced corrugated board is shown coming from the usual bridge. It passes over guide rolls 12 and its outer liner board surface receives a coating of wax from an applicator roll 14. The wax preferably is a special type of paraffin having a melting point of approximately 127 degrees F. It is applied in a quantity approximately 30% to 40% of the dry weight of the liner board. The corrugating medium has been previously impregnated with asphalt approximating 30% of the dry weight of the corrugating medium.

The web 10 then wraps around a primary preheating roll 16 with the coated surface in contact with the roll. A guide roll 18 then directs web 10 to a secondary preheating roll 20. The web then passes to a conventional glue roll 22 and thence to conventional combining and hot plate stations of the corrugator. These comprise a hold down belt 21 passing over a tail roll 23 and pressing the single-face web 10 against the opposite web of liner board 32. This board, in turn is pressed against a hot plate.

A roll 30 supplies a web 32 of liner board to a primary preheating roll 34, thence over guide rolls 36 to a wax applicator roll 38 which applies to what will be the outer surface of the final corrugated board, a coating of paraffin wax similar to that applied to the Web and approximating to 40% of the dry Weight of the web 32.

A guide roll 40 coacts with a guide roll 42 to bring the coated surface of the web 32 lightly into contact with itself over the preheater roll 34. Since the contacting portions are moving in opposite directions there will be some transfer of wax from the coated to the uncoated portion of the web so that the application of wax may be said to take place in two stages.

The guide roll 42 coacts with a guide roll 44 to Wrap the Web 32 around a secondary preheating roll 46 with the coated side in contact with the roll. From the guide roll 44 the Web 32 goes to the conventional combining and hot plate stations, where it is adhered to the corrugated side of the Web 10.

In the case of both webs, considerable penetration of wax into the liner board occurs not only at the wax applicator but during contact with the heater rolls. In the case of the web 32, this penetration is deliberately restrained so as not to strike entirely through the board, so that its inner surface remains receptive to the glue at the combining station. The hot plate section, however, completes the penetration so that the final double-faced corrugated board is completely impregnated, the liners With wax and the corrugating medium with asphalt. Compression tests indicate that the board thus produced has about greater stacking strength than conventional board of the same dry weight of liners and corrugating material.

With wax of the parafiin type having a melting point of 127 F. and at a web speed of approximately feet per minute the rolls 16, 20, 34 and 46, as well as the hot plate 25 will be kept at 325 to 350 by steam at psi. Clearly electrical, radiant or other heating means may be used.

For some purposes, only one side of the ultimate container need be waxed, in such case it is only necessary to cut the steam from the appropriate heating rolls and eliminate the wax supply in the appropriate applicator roll. The hot plate, of course, is used in conventional operations.

The above described board, and process and apparatus are susceptible of considerable variation. It is not intended therefore, that this invention be limited to the precise details herein disclosed but only as set forth in the subj oined claim.

What is claimed is:

Apparatus for producing moisture and liquid resistant corrugated board comprising means to advance a continuous Web of single face corrugated board, said board comprising a liner adhered to the crests of a corrugated web; means to advance a continuous web of liner board; means for applying a coating of wax to the exterior surface of the liner of said single faced board; means for applying a coating of wax to the exterior surface of said second named liner board; means to adhere the interior surface of said second named liner board to the crests exposed on said corrugated web; and means to heat the combined board to cause said wax coatings to penetrate inwardly toward the crests of said corrugated web.

References Cited in the file of this patent UNITED STATES PATENTS 1,362,698 Higgons Dec. 21, 1920 1,497,809 Sutherland June 17, 1924 1,519,280 Wandel Dec. 16, 1924 1,519,281 Wandel Dec, 16, 1924 1,592,824 Fairchild July 20, 1926 1,770,757 Maston July 15, 1930 2,513,708 Belcher July 4, 1950 2,568,349 McKee Sept. 18, 1951 2,723,923 Munters Nov. 15, 1955 2,967,116 Hollinger et al. Jan. 3, 1961 2,982,333 Little May 2, 1961 

